Nutlet micromorphology of Iranian Nepeta (Lamiaceae) species

To evaluate nutlets characteristics for systematic relationships, a comprehensive morphological and micro-morphological study of the nutlets of 16 Iranian taxa of Nepeta (Lamiaceae) was conducted using scanning electron microscopy (SEM). Differences in surface ornamentation, size, shape and color were observed between the species. The studied taxa were categorized in two basic types based on surface ornamentation: non-sculptured (smooth-type) and sculptured nutlets. The non-sculptured nutlets type could be further divided into four sub-types, including smooth, granulate, undulate-cellular and reticulate. In the sculptured nutlets, three subtypes of tuberculate, tuberculate-cellular and verrucate were recognized. The shape of nutlets were described as oblong, ovoid-oblong, oblong-linear, to elliptic-oblong and their size range are 1.2–2.0 mm in length and 0.5–2.0 mm in width. Based on micrographs, the areole form and location were defined as bi-lobed, straight, basal, sub-basal or lateral. Nutlet micromorphological characteristics such as surface ornamentation can be useful for classification and identification of e.g. medicinal species of Nepeta in Iran.